Hermetic compressor

ABSTRACT

A hermetic compressor includes: a hermetic case; a frame configured to be received in the hermetic case, a drive unit and a compression unit arranged at lower and upper sides of the frame, respectively; a rotating shaft mounted to the frame and configured to transmit a rotational force of the drive unit to the compression unit and having an upper eccentric portion connected to the upper compression unit; and a connecting rod configured to be coupled to the eccentric portion. An oil bank may be formed at a surface of the eccentric portion of the rotating shaft that comes into contact with the connecting rod.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 toKorean Patent Application No. 2005-65184, filed Jul. 19, 2005, entirecontents of which are incorporated herein by reference. This applicationmay also be related to commonly owned U.S. patent application Ser. No.11/199,170, filed Aug. 9, 2005, as well as commonly owned U.S. patentapplication Ser. No. 11/232,936, filed Sep. 23, 2005, the contents ofeach of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hermetic compressor, and, moreparticularly, to a hermetic compressor having an improved oil supplystructure capable of supplying a sufficient amount of oil into a spacedefined between an eccentric portion of a rotating shaft and aconnecting rod.

2. Description of the Related Art

Japanese Patent Laid-Open Publication No. 63-85270 describes aconventional hermetic compressor in which oil is supplied intorespective drive parts of the compressor by use of a rotationalcentrifugal force of a rotating shaft. According to the conventionalstructure for lubricating an eccentric portion of the rotating shaft, itis impossible to supply a sufficient amount of oil to the frictionalregion between the eccentric portion and a connection rod because an oilreceiving gap between the connecting rod and the eccentric portion isextremely narrow. This results in insufficient lubrication, which causesexcessive wear of the compressor components.

In particular, if a drive motor stops, the oil, which serves as alubricant between the rotating shaft and the connecting rod, flowsdownward while only an extremely small amount of oil remains. As aresult, the rotating shaft inevitably rotates with little or no oillubrication until oil is again supplied when the compressor initiallyoperates. As a result, wear of the compressor parts increases, as doesthe noise generated by the compressor.

Furthermore, since the eccentric portion of the rotating shaft exhibitspoor lubrication when the maximum compression load is applied as thepiston reaches a top dead point, durability and operational reliabilityof the rotating shaft are severely damaged.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve the aboveproblems. It is an aspect of the invention to provide a hermeticcompressor capable of supplying a sufficient amount of oil into africtional region between an eccentric portion of a rotating shaft and aconnecting rod.

To this end, a first non-limiting aspect of the present inventionprovides a hermetic compressor, including: a hermetic case; a frameconfigured to be received in the hermetic case, a drive unit and acompression unit arranged at lower and upper sides of the frame,respectively; a rotating shaft mounted to the frame and configured totransmit a rotational force of the drive unit to the compressional unitand having an upper eccentric portion connected to the upper compressionunit; and a connecting rod configured to be coupled to the eccentricportion, wherein an oil bank is formed at a surface of the eccentricportion of the rotating shaft that comes into contact with theconnecting rod.

Another non-limiting aspect of the present invention provides a hermeticcompressor, including: a case; a drive unit adapted to be received inthe case; a compression until adapted to be received in the case; arotating shaft configured to transmit a rotation a1 force of the driveunit to the compression unit, the rotating shaft including at least aneccentric portion; a connecting rod configured to be coupled to theeccentric portion and an oil bank positioned at a surface of theeccentric portion.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the exemplary embodimentsof the invention will become apparent and more readily appreciated fromthe following description of the embodiments, taken in conjunction withthe accompanying drawings, of which:

FIG. 1 is a sectional view showing a non-limiting example of an oilsupply structure for an eccentric portion of a rotating shaft;

FIG. 2 is a sectional view showing a non-limiting example of an interiorconfiguration of a hermetic compressor including an eccentric portion ofa rotating shaft;

FIG. 3 is a sectional view showing an oil supply configuration includingan oil bank formed at the eccentric portion of the rotating shaftaccording to a second non-limiting embodiment of the present invention;

FIGS. 4A to 4C are sectional views showing an oil supply configurationincluding an oil bank formed at the eccentric portion of the rotatingshaft according to a third non-limiting embodiment of the presentinvention;

FIGS. 5A to 5C are sectional views showing an oil supply configurationincluding an oil bank formed at the eccentric portion of the rotatingshaft according to a fourth non-limiting embodiment of the presentinvention;

FIG. 6 is a sectional view showing the a non-limiting example of thepositional relationship between the rotating shaft, connecting rod, andpiston when the piston reaches a top dead point;

FIGS. 7A to 7C are sectional views showing an oil supply configurationincluding an oil bank formed at the eccentric portion of the rotatingshaft according to a fifth non-limiting embodiment of the presentinvention; and

FIGS. 8A to 8C are sectional views showing an oil supply configurationincluding an oil bank formed at the eccentric portion of the rotatingshaft according to a sixth non-limiting embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout. The embodiments are described below to explain the presentinvention by referring to the figures.

Referring to FIG. 1, a rotating shaft of a hermetic compressor isillustrated in sectional view. As shown in FIG. 1, an oil pickup member(not shown) raises oil gathered in the bottom of a hermetic case whenrotating shaft 10 rotates. To ensure smooth rising of the oil, the oilpickup member (not shown) may be connected to a lower end of therotating shaft 10, and an eccentric channel (not shown) may be formed inthe rotating shaft 10 at the top of the oil pickup member. The eccentricchannel (not shown) may be eccentrically extended relative to the centerof the rotating shaft. Also, a spiral channel 50, i.e., a spiral groove,may be formed at an outer circumferential surface of the rotating shaftto be connected to the eccentric channel.

The rotating shaft 10 may include an eccentric portion 20, which mayhave a hollow channel 30 centrally defined therein. To supply oil to apiston (not shown), a lower end of the hollow channel 30 may beconnected to an upper end of the spiral groove 50 and an upper end ofthe hollow channel 30 may be open. A connection path 40 may be formed ata middle height of the hollow channel 30 to communicate with the hollowchannel 30. Specifically, the connection path 40 may be extended in aradial direction of the eccentric portion 20 to supply oil to a contactregion between the eccentric portion 20 and a connecting rod (notshown).

During operation of the hermetic compressor having the above-describedconfiguration, if the rotating shaft rotates in a predetermineddirection, oil is suctioned upward via the oil pickup member inaccordance with rotation of the rotating shaft. Subsequently, the oilmoves upward along the oil channel and the spiral groove of the rotatingshaft due to the rotational centrifugal force of the rotating shaft. Inthis way, it is possible to transfer oil to respective frictional andhigh temperature regions.

A part of the rising oil is scattered upward via the hollow channel 30formed in the eccentric portion 20, so that it is transferred to thefrictional and high-temperature regions while flowing downward, therebyserving to lubricate and cool those regions. Also, a part of the oiltransferred into the hollow channel 30 of the eccentric portion 20 isintroduced into the connection path 40, thereby serving to lubricate andcool a frictional contact region between the eccentric portion 20 andthe connecting rod.

The overall configuration of the hermetic compressor having an improvedrotating shaft according to a non-limiting aspect of the presentinvention will be explained in detail with reference to FIG. 2. As shownin FIG. 2, the hermetic compressor may include: a frame 120 mounted in ahermetic case 100 by interposing a plurality of dampers 110; acompression unit 200 disposed on the top of the frame 120; and a driveunit 300 arranged beneath the frame 120 to drive the compression unit200.

The hermetic compressor may further include a rotating shaft 400 fortransmitting a rotational force of the drive unit 300 to the compressionunit 200. The rotating shaft 400 may be vertically extended and may berotatably supported by a shaft supporting portion of the frame 120. Therotating shaft 400 may include an eccentric portion 410 eccentricallyformed at an upper end thereof relative to the center of the rotatingshaft 400. The eccentric portion 410 may be used to connect the rotatingshaft 400 to the compression unit 200. The rotating shaft 400 may alsoinclude a bearing supporting portion 420 formed at a lower end of theeccentric portion 410. The bearing supporting portion 420 of therotating shaft 400 may have an outer diameter larger than the remainingportion of the rotating shaft 400 so that it can be supported on the topof the frame 120. A thrust bearing 430 may be interposed between a lowersurface of the bearing supporting portion 420 and an upper surface ofthe frame 120 to support an axial load of the rotating shaft 400 whilefacilitating rotation of the rotating shaft 400.

The drive unit 300 may include a rotor 310 coupled to an outer surfaceof the rotating shaft 400 to rotate along with the rotating shaft 400,and a stator 320 affixed to an outer circumference of the rotor 310. Thecompression unit 200 may include a cylinder 210 and a cylinder head 220which define a refrigerant compression chamber, a piston 230 arranged toreciprocate in the cylinder 210 to compress a refrigerant, and aconnecting rod 250 having one end connected to a pin 240 of the piston230 and the other end connected to the eccentric portion 410 of therotating shaft 400. With this configuration, when the rotating shaft 400rotates in accordance with operation of the drive unit 300, theeccentric portion 410 of the rotating shaft 400 and the connecting rod250 convert rotating motion into linear reciprocating motion, so thatthe piston 230 is moved forward or backward to compress a refrigerant.

The hermetic compressor of the present invention having theabove-described configuration may contain a predetermined amount of oil(L) in the bottom of the hermetic case 100 for the lubrication andcooling of respective drive parts. An oil pickup member 510 may beconnected to a lower end of the rotating shaft 400 so that the oil (L)gathered in the bottom of the hermetic case 100 moves upward, therebybeing transferred to the respective drive parts by use of a rotationalcentrifugal force of the rotating shaft 400. An eccentric hole 520 maybe formed in the rotating shaft 400 above the oil pickup member 510 sothat it may be spaced apart from the center of the rotating shaft 400 bya predetermined distance. The eccentric hole 520 may be used to move theoil (L) upward. Also, a spiral groove 530 may be formed at an outercircumferential surface of the rotating shaft 400 to communicate withthe eccentric hole 520.

FIG. 3 is a sectional view showing an oil supply structure according toa second non-limiting embodiment of the present invention. As shown inFIG. 3, the spiral groove 530 may have a predetermined depth, and may beformed at an outer circumferential surface of the shaft 400. Thereby,oil can be guided upward along the spiral groove 530 when the rotatingshaft 400 rotates. The upwardly moved oil serves to lubricate and coolboth the outer surface of the rotating shaft 400 and the inner surfaceof the shaft supporting portion.

A communication bore 540 may be formed in a radial direction of therotating shaft 400 at an upper location of the outer surface of therotating shaft 400 so that the oil can be guided to the eccentricportion 410 after moving upward via the spiral groove 530. The eccentricportion 410 may be provided with a hollow channel 550. A lower end ofthe hollow channel 550 may be connected to the communication bore 540and an upper end of the hollow channel 500 may be open, so that the oilcan be supplied to the piston. A connection path 560 may be formed in aradial direction of the eccentric portion 410 at a middle height of thehollow channel 550 to communicate with the hollow channel 550, so thatthe oil can be supplied to a contact region between the eccentricportion 410 and the connecting rod (not shown).

An oil bank 600 may be formed around an outer circumferential surface ofthe eccentric portion 410 where the eccentric portion 410 comes intocontact with the connecting rod. The oil bank 600 may be formed at thesame location as the connection path 560, and may be formed as of acircumferential groove having a predetermined width and depth suitableto receive the oil discharged from the connection path 560.

Now, a process for supplying oil into the eccentric portion 410 of therotating shaft 400 according to the above non-limiting embodiment of thepresent invention will be explained. First, if the compressor is driven,the oil gathered in the bottom of the compressor moves upward in avortex flow form by successively passing through the oil pickup member,the eccentric hole, and the spiral groove due to the rotationalcentrifugal force of the rotating shaft. Then, the upwardly moved oilreaches the hollow channel of the eccentric portion by way of thecommunication bore, so that it is scattered upward via the hollowchannel, thereby being transferred to frictional and high-temperatureregions. A part of the rising oil is introduced into the connection pathto reach the oil bank, thereby serving to lubricate and cool africtional region between the eccentric portion and the connecting rod.

In particular, if the rotating shaft begins to rotate as the compressorinitially operates, the remainder of the oil inside the oil bank isforced out of the oil bank by a centrifugal force. Thereby, the oil canserve to appropriately lubricate the eccentric portion of the rotatingshaft even during a transition period until new oil is again supplied.This eliminates a risk of wear at the contact region between theeccentric portion and the connecting rod, achieving an improvement inthe performance of the compressor.

Referring to FIGS. 4A to 4C, an oil supply structure according to athird non-limiting embodiment of the present invention is illustrated insectional view. In the third non-limiting embodiment, an oil path mayalso be provided at an upper or lower location of the eccentric portion.

As shown in FIG. 4A, an upper linear groove 700, having a predeterminedwidth and depth, may be formed at the outer circumferential surface ofthe eccentric portion 410 so that it extends from an upper end of theoil bank 600 to an upper end of the eccentric portion 410. With the useof the upper linear groove 700, after being supplied into the oil bank600 through the connection path 560 of the eccentric portion 410, oil isable to move to the upper end of the eccentric portion 410 by acentrifugal force of the rotating shaft 400, thereby serving tolubricate a frictional region between the eccentric portion 410 and theconnecting rod. This has the effect of expanding an oil path.

Additionally, as shown in FIG. 4B, a lower linear groove 710, having apredetermined width and depth, may be additionally formed at the outercircumferential surface of the eccentric portion 410 so that it extendsfrom a lower end of the oil bank 600 to a lower end of the eccentricportion 410. The lower linear groove 710 allows the oil, which issupplied into the oil bank 600 through the connection path 560, to movedownward along the eccentric portion 410. This expands the flow path ofoil serving as a lubricant for the frictional region between theeccentric portion 410 and the connecting rod, and facilitates effectivedischarge of foreign substances.

Alternatively, a single spiral groove for moving oil formed at the outercircumferential surface of the eccentric portion. However, this spiralgroove is designed to move oil in only a rotating direction of therotating shaft due to a limitation in geometrical characteristicsthereof. That is, oil is allowed to move upward in the spiral grooveonly when the spiral groove is formed in a direction opposite to therotating direction of the rotating shaft. Unlike the spiral groove, theabove-described linear grooves of the present invention are not affectedby geometrical characteristics, and allow oil to move upon receiving arotational centrifugal force of the rotating shaft, regardless of therotating direction of the rotating shaft.

Referring to FIG. 4C, to allow the oil (which enters the oil bank 600 bythe centrifugal force of the rotating shaft 400), to more effectivelymove to upper and lower portions of the eccentric portion 410, upper andlower inclined grooves 720 and 730 (serving as oil paths) may be formedabove and beneath the oil bank 600. The upper groove 720 may be inclinedin a direction opposite to the rotating direction of the rotating shaft400 as designated by an arrow. The lower groove 730 may be inclined inthe same direction as the rotating direction of the rotating shaft 400.

When oil moves along the upper and lower inclined grooves as statedabove, the inclinations of the grooves provide resistance. Because theresistance of the path increases as the incline increases, a rotationalcentrifugal force of the rotating shaft can be used to overcome theincreased resistance, resulting in a gradual reduction in the flow rateof the oil. Thus, it may be preferable to set an appropriate inclinationof the grooves in consideration of the amount and flow rate of the oiland the stress applied to the frictional region.

Referring to FIGS. 5A to 5C, an oil supply structure according to afourth non-limiting embodiment of the present invention is illustrated.Unlike the third embodiment in which oil is supplied into the oil bankvia the connection path of the eccentric portion, oil may be suppliedinto the oil bank as it is scattered from the hollow portion to movedownward into the oil bank according to the fourth non-limitingembodiment.

As shown in FIG. 5A, the eccentric portion 410 may be internally formedwith the hollow channel 550 having an open upper end, so that oil movesupward to the upper end of the eccentric portion 410. Also, the oil bank600 may have a circumferential groove form and may be formed at theouter circumferential surface of the eccentric portion 410 so that theoil moves along the oil bank 600.

Referring to FIG. 6, if the piston 230 reaches a top dead point (therebyreaching the maximum compression load), the maximum compression load maycause location (A) of the eccentric portion 410 to undergo maximumstress. Thus, it may be preferable to supply a sufficient amount of oilto location (A) because location (A) is most easily worn. Since location(A) is also where the rotational centrifugal force of the rotating shaftis applied to the maximum extent, the maximum amount of oil may bescattered and dropped via the hollow channel 550 so as to be gathered inlocation (A).

For this reason, in the present embodiment, a spiral groove 810 may beformed to extend from the upper end of the eccentric portion 410 to theupper end of the oil bank 600. Therefore, oil, which may be scatteredand dropped from the hollow channel 550 of the eccentric portion 410,moves downward along the spiral groove 810 to sufficiently lubricate andcool the frictional region between the eccentric portion and theconnecting rod. So that the oil smoothly moves downward along the spiralgroove 810 regardless of the rotational centrifugal force of therotating shaft 400, it may be preferable that the spiral groove 810 isinclined in the same direction as the rotating direction of the rotatingshaft 400.

Referring to FIG. 5B, a lower spiral groove 820 may also be formedbeneath location (A). The lower spiral groove 820 may be positionedbeneath the oil bank 600 to extend from the lower end of the oil bank600 to the lower end of the eccentric portion 410, so that the oilinside the oil bank 600 moves downward to the lower end of the eccentricportion 410. Through this configuration, lubrication of the contactregion between the eccentric portion and the connecting rod may beeasily achieved. The lower spiral groove 820 may expand the area of theoil path and may also be used as a discharge port for foreignsubstances, especially fine particulates. Preferably, the lower spiralgroove 820 may also be inclined in the same direction as the rotatingdirection of the rotating shaft 400 to ensure that the oil smoothlymoves downward along the spiral groove 820, regardless of the rotationalcentrifugal force of the rotating shaft 400.

Referring to FIG. 5C, to effectively disperse stress generated in thefrictional region between the eccentric portion and the connecting rod,more particularly, generated at location (A), a groove 830 may be formedbeneath the oil bank 600. The groove 830 may extend from a region, whichmay be spaced apart from location (A) by a predetermined distance, tothe lower end of the eccentric portion. The lower groove 830 serves notonly to expand the area of the oil path and to discharge foreignsubstances as stated above, but also to effectively disperse the stressapplied to the eccentric portion, thereby achieving an improvement inthe durability of the rotating shaft.

Referring to FIGS. 7A to 7C, an oil supply structure according to afifth non-limiting, embodiment of the present invention is illustratedin sectional view. The fifth embodiment may include a connection pathformed at the oil bank to communicate with the hollow channel of theeccentric portion, in addition to the configuration described withreference to FIGS. 5A to 5C.

With the present embodiment, oil may be scattered and dropped from thehollow channel 550 of the eccentric portion 410 by the centrifugal forceof the rotating shaft, thereby causing the oil to move downward alongthe spiral groove. Remaining oil may enter the connection path 560 tomove into the oil bank 600. Thereby, a sufficient amount of oil may besupplied to the frictional region between the eccentric portion 410 andthe connecting rod, resulting in a reduction in wear of parts due tofriction.

Referring to FIGS. 8A to 8C, a sixth non-limiting embodiment of thepresent invention is illustrated. The sixth non-limiting embodiment maybe applied to any of the above-described embodiments. Specifically, thepresent embodiment may include two or three oil banks having theconfigurations described in the third to fifth embodiments. Accordingly,the number connection paths may be increased.

As shown in FIGS. 8A to 8C, the eccentric portion 410, as described inthe third to fifth embodiments, may also be provided with a second oilbank 610. The second oil bank 610 may be located above the oil bank 600and may include a circumferential groove formed at the outercircumferential surface of the eccentric portion 410. A secondconnection path 560 a may be formed at the second oil bank 610 tocommunicate with the hollow channel 550 of the eccentric portion 410.With this non-limiting exemplary configuration, a plurality of oil pathsmay be formed at the frictional region between the eccentric portion andthe connecting rod to achieve satisfactory oil lubrication, whichreduces wear in the compressor.

As apparent from the above description, the present invention providesan improved oil supply configuration in which an oil bank may be formedaround an eccentric portion of a rotating shaft at a position of aconnection path, thereby achieving more effective lubrication andcooling in a frictional region between the eccentric portion and aconnecting rod. Such effective lubrication and cooling of the rotatingshaft ensures a high reliability of the compressor.

In particular, oil gathered in the oil bank acts to smoothly lubricatecontact surfaces of both the eccentric portion and the connecting rodwhen the compressor initially operates. Thereby, it is possible toprevent wear of the contact surfaces and to improve the performance ofthe compressor. Further, according to the present invention, an oil pathmay be formed at a lower region of the eccentric portion to dischargeforeign substances, thereby preventing locking between the eccentricportion and the connecting rod.

Although embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A hermetic compressor, comprising: a hermetic case; a frameconfigured to be received in the hermetic case, a drive unit and acompression unit arranged at lower and upper sides of the frame,respectively; a rotating shaft mounted to the frame and configured totransmit a rotational force of the drive unit to the compression unitand having an upper eccentric portion connected to the upper compressionunit; and a connecting rod configured to be coupled to the eccentricportion, wherein an oil bank is formed at a surface of the eccentricportion of the rotating shaft that comes into contact with theconnecting rod.
 2. The hermetic compressor according to claim 1, whereinthe oil bank includes a circumferential groove formed at an outercircumferential surface of the eccentric portion.
 3. The hermeticcompressor according to claim 2, wherein the eccentric portion of therotating shaft includes: a hollow channel having an open upper endconfigured to scatter oil therefrom; and a connection path formed in aradial direction of the eccentric portion to communicate with the hollowchannel so that oil is supplied to at least one contact portion betweenthe eccentric portion and the connecting rod.
 4. The hermetic compressoraccording to claim 3, wherein the connection path is formed at the oilbank such that oil supplied into the connection path effectively remainsin the oil bank.
 5. The hermetic compressor according to claim 4,wherein a linear groove is formed at an outer circumferential surface ofthe eccentric portion to extend from an upper end of the oil bank to theupper end of the eccentric portion, thereby serving as an oil path toallow oil discharged from the connection path to move upward along theeccentric portion.
 6. The hermetic compressor according to claim 5,wherein a linear groove is formed at the outer circumferential surfaceof the eccentric portion to extend from a lower end of the oil bank to alower end of the eccentric portion, thereby serving as an oil path toallow the oil discharged from the connection path to move downward alongthe eccentric portion.
 7. The hermetic compressor according to claim 4,wherein; an upper inclined groove is formed above the oil bank to extendin a direction opposite to a rotating direction of the rotating shaft,and a lower inclined groove is formed beneath the oil bank to extend inthe rotating direction of the rotating shaft.
 8. The hermetic compressoraccording to claim 2, wherein the eccentric portion includes: a hollowchannel having an open upper end to allow oil to be scattered therefrom;and an inclined groove formed at an outer circumferential surface of theeccentric portion to extend from the upper end of the eccentric portionto an upper end of the oil bank in a rotating direction of the rotatingshaft, thereby allowing the oil scattered from the upper end of thehollow channel to move downward to a location of the eccentric portionwhere a maximum centrifugal force is applied when a piston reaches a topdead point in a cylinder.
 9. The hermetic compressor according to claim8, wherein the eccentric portion further includes: an inclined grooveformed at the outer circumferential surface of the eccentric portion toextend from a lower end of the oil bank to a lower end of the eccentricportion in the same direction as the rotating direction of the rotatingshaft, thereby allowing the oil remaining in the oil bank to movedownward to the location of the eccentric portion where the maximumcentrifugal force is applied when the piston reaches the top dead pointin the cylinder.
 10. The hermetic compressor according to claim 8,wherein the eccentric portion further includes: an inclined grooveformed at the outer circumferential surface of the eccentric portion toextend from a lower end of the oil bank to a lower end of the eccentricportion in the rotating direction of the rotating shaft, therebyenabling the oil remaining in the oil bank to move downward to a regionwhich is spaced apart from the location of the eccentric portion wherethe maximum centrifugal force is applied when the piston reaches a topdead point in the cylinder.
 11. The hermetic compressor according to anyone of claims 8 to 10, wherein a connection path is formed in a radialdirection of the eccentric portion to communicate with both the hollowchannel and the oil bank, so that the oil is supplied to at least onecontact region between the eccentric portion and the connecting rod. 12.The hermetic compressor according to claim 11, wherein the eccentricportion further includes a second oil bank, which includes acircumferential groove formed at the outer circumferential surface ofthe eccentric portion above the oil bank.
 13. The hermetic compressoraccording to claim 12, wherein the eccentric portion further includes asecond connection path formed in a radial direction of the eccentricportion to communicate with both the hollow channel and the second oilbank, so that the oil flowing in the hollow channel is introduced intothe second oil bank.
 14. The hermetic compressor according to any one ofclaims 5 to 8, wherein the eccentric portion further includes a secondoil bank including a circumferential groove formed at the outercircumferential surface of the eccentric portion above the oil bank. 15.The hermetic compressor according to claim 14, wherein the eccentricportion further includes a second connection path formed in a radialdirection of the eccentric portion to communicate with both the hollowchannel and the second oil bank, so that the oil flowing in the hollowchannel is introduced into the second oil bank.
 16. A hermeticcompressor, comprising: a case; a drive unit adapted to be received inthe case; a compression unit adapted to be received in the case; arotating shaft configured to transmit a rotational force of the driveunit to the compression unit, the rotating shaft including at least oneeccentric portion; a connecting rod adapted to be coupled to the atleast one eccentric portion; and an oil bank positioned at a surface ofthe at least one eccentric portion.
 17. The hermetic compressoraccording to claim 16, wherein the oil bank is positioned at a surfaceof the at least one eccentric portion that contacts the connecting rod.18. The hermetic compressor according to claim 16, further comprising aconnection path formed at the at least one eccentric portion to supplyoil to at least one contact portion between the at least one eccentricportion and the connecting rod.